It didn't go Madison Keys' way this day. But the 17-year-old did reach the third round of a Slam for the first time. Lucas Dawson, Getty Images

In this photo released by Tennis Australia Angelique Kerber of Germany has some birthday cake. Fiona Hamilton, AP

Ballkids dry the court during a rain delay in the Kerber-Keys match Manan Vatsayana, AFP/Getty Images

In this photo released by Tennis Australia Russia's Svetlana Kuznetsova holds a baby wombat in the players lounge. Fiona Hamilton, AP

She is a fan of Australian tennis. We think. Greg Wood, AFP/Getty Images

It was way hot on Day 4, and this is how Andreas Seppi of Italy cooled off after defeating Denis Istomin of Uzbekistan 7-6 (7-4), 5-7, 6-7 (3-7), 7-6 (7-3), 6-2. Temperatures reached 106 degrees at Melbourne Park. Fiona Hamilton, AP

After a singles win Serena Williams, left, returned to the court to win a doubles match with sister Venus. They defeated Camila Giorgi of Italy and Stefanie Voegele of Switzerland 6-3, 6-1. Aaron Favila, AP

Bernard Tomic of Australia thrilled the home crowd with a come-from-behind 6-7 (4-7), 7-5, 7-6 (7-3), 7-6 (10-8) win against Daniel Brands of Germany. Next up for Tomic is Roger Federer. William West, AFP/Getty Images

Serena Williams celebrates her 6-2, 6-0 second-round victory against Garbine Muguruza of Spain, showing no signs of an injured right ankle. William West, AFP/Getty Images

A bird's-eye view of the best weapon in the game, Serena's serve. Quinn Rooney, Getty Images

Sam Querrey talks with Brian Baker after Baker was forced to retire from their match because of a knee injury. Baker tore his lateral meniscus and has a locked knee. He'll need surgery and about four months to recover. Chris Hyde, Getty Images